Real time processor based on FPGA and DSP for atmospheric parameters evaluation from closed-loop data of adaptive optical system

To realize the measurement of atmospheric parameters, a kind of real time processor based on FPGA and DSP is proposed and designed. When Adaptive Optical (AO) system is close-loop, the FPGA reconstructs the open-loop Zernike coefficients from the close-loop data of residual slopes and corrected voltages, which are used for the later complex statistical calculations of the coherence length r0, the outer scale L0, the wind speed v and the coherence time t0 by the DSP. The errors of the open-loop Zernike coefficients reconstructed by FPGA are less than 3x10 -8 λ ( λ is the wavelength). The errors of the atmospheric parameters computed by DSP are less than 7.8x10 -8 cm (r0), 5.3x10 −5 m (L0), 7.5x10 -7 m/s (v) and 4.0x10 -6 ms (t0), respectively. For 127-element AO system at 1.8m telescope with 2000Hz sampling frequency, the processing latencies of FPGA and DSP are 19.65us and 553.8ms respectively, and the refresh time of atmospheric parameters is 1.85s. The results show that the proposed processor can be used to measure the real time atmospheric parameters.